Ionic liquids in analytical chemistry

Ionic liquids (ILs) are composed entirely of ions and they possess fascinating properties, including low volatility, tunable viscosity and miscibility, and electrolytic conductivity, which make ILs unique and useful for many applications in chemical analysis. The dramatic increase in the number of publications on ILs is indicative of the tremendous interest in this field from analytical chemists. This review summarizes recent efforts in the major subdisciplines of analytical chemistry, including extractions, gas chromatography, liquid chromatography, capillary electrophoresis, mass spectrometry, electrochemistry, sensors, and spectroscopy.     

Imprinted polymer particles for selenium uptake: synthesis, characterization and analytical applications

This work reports the preparation of molecularly imprinted polymer (MIP) particles for selective extraction and determination of selenium ions from aqueous media. Polymerization was achieved in a glass tube containing SeO₂, o-phenylenediamine, 2-vinylpyridine (VP), ethyleneglycoldimethacrylate (EDMA), 2,2′-azobisisobutyronitrile (AIBN). The polymer block obtained was ground and sieved (55-75 μm) and the Se-o-phenylenediamine complex was removed from polymer particles by leaching with 2 M of HCl, which leaves a cavity in the polymer particles. The polymer particles both prior to and after leaching have been characterized by IR and thermogravimetric (TG) studies. The effect of different parameters, such as pH, extraction time, type and least amount of eluent for elution of complex from polymer were evaluated. Extraction efficiencies >99% were obtained by elution of the polymers with 15 mL of methanol-acetonitrile mixture (1:2, v/v). The limit of detection of the proposed method followed by hydride generation atomic absorption spectroscopy (HG-AAS) was found to be 3.3 μg L⁻¹ and a dynamic linear range (DLR) of 10-200 μg L⁻¹ was obtained. The relative standard deviations (R.S.D.s) at 30.0 μg L⁻¹ of Se were below than 8.1%. The influence of various cationic interferences on percent recovery of complex was studied. The method was applied to the recovery and determination of selenium in different real samples.     

Ionic liquid incorporated polystyrene resin for solid-phase peptide synthesis

Ionic liquid (IL) resins with an ionic liquid environment on solid support were prepared by immobilizing ionic liquid spacers on polystyrene (PS) resin. The properties of IL resins were dramatically changed as the anions of IL were exchanged. The performance of IL resins for solid-phase peptide synthesis (SPPS) was evaluated by measuring coupling kinetics of the first amino acid and synthesizing several peptides on IL resins.     

Wavelet transform applications in analytical chemistry

The wavelet transform has been established with the Fourier transform as a data-processing method in analytical chemistry. The main fields of application in analytical chemistry are related to denoising, compression, variable reduction, and signal suppression. Analytical applications were selected showing prospects and limitations of the wavelet transform. An important aspect consists in showing the advantage of wavelet transform over Fourier transform with respect to dual localization of a signal in both the original and the transformed domain enabling principal new application fields in comparison with Fourier transform.     

Ion imprinted polymer particles: synthesis, characterization and dysprosium ion uptake properties suitable for analytical applications

Dysprosium(III) ion imprinted polymer particles were prepared by the copolymerization of styrene monomers and a crosslinking agent divinylbenzene in the presence of dysprosium(III)-5,7-dichloroquinoline-8-ol-4-vinyl pyridine ternary complex wherein dysprosium(III) ion is the imprint ion and is used to form the imprinted polymer. The dysprosium(III) ion was removed from polymer particles by leaching with 1:1 HCl which leaves a cavity in the polymer particles. The polymer particles both prior to and after leaching have been characterized by IR, TGA, DTA and XRD studies. The leached particles selectively preconcentrated dysprosium ion from dilute aqueous solutions as determined spectrophotometrically using Arsenazo-I as reagent. The optimum pH value for quantitative enrichment is 6-9 and desorption can be achieved by using 25 ml of 1 mol/l of HCl. The retention capacity of the polymer particles was found to be 40.15 mg/g, which is much higher than MIPs prepared by other imprinting techniques. The dysprosium ion imprinting polymer gave 40 times higher distribution ratio for dysprosium ion compared to blank polymer. More significantly the selectivity coefficients of dysprosium compared to other lanthanides results in enhancement by 60-180-fold. The separation factors with respect to other selected lanthanides were also compared with liquid-liquid extractive separation using di-2-ethylhexyl phosphoric acid (D2EHPA) as extractant. The selectivity of dysprosium ion imprinting polymer (IIP) particles for dysprosium over yttrium is much higher and comparable in case of Nd and Lu when compared to conventional extractant such as D2EHPA in liquid-liquid extraction (LLE). Five replicate determinations of 50 μg of dysprosium present in 250 ml of sample gave a mean absorbance of 0.150 with a relative standard deviation of 2.42%. The detection limit corresponding to three times the standard deviation of the blank was found to be 2 μg/250 ml.     

Nitroxides: applications in synthesis and in polymer chemistry

This Review describes the application of nitroxides to synthesis and polymer chemistry. The synthesis and physical properties of nitroxides are discussed first. The largest section focuses on their application as stoichiometric and catalytic oxidants in organic synthesis. The oxidation of alcohols and carbanions, as well as oxidative C-C bond-forming reactions are presented along with other typical oxidative transformations. A section is also dedicated to the extensive use of nitroxides as trapping reagents for C-centered radicals in radical chemistry. Alkoxyamines derived from nitroxides are shown to be highly useful precursors of C-centered radicals in synthesis and also in polymer chemistry. The last section discusses the basics of nitroxide-mediated radical polymerization (NMP) and also highlights new developments in the synthesis of complex polymer architectures.     

Recent applications of digital computers in analytical chemistry

Minicomputers are finding increasing use for the control and operation of analytical instruments. This role is likely to be shared in the near future with dedicated microcomputers. Applications of computers to electroanalytical chemistry, Fourier transform techniques, spectroscopy, rapid-reaction kinetics, equilibrium constants, studies of analytical methods and to literature searching, are also discussed.     

State-of-the-art anodes of potassium-ion batteries: synthesis,chemistry, and applications

The growing demand for green energy has fueled the exploration of sustainable and eco-friendly energy storage systems. To date, the primary focus has been solely on the enhancement of lithium-ion battery (LIB) technologies. Recently, the increasing demand and uneven distribution of lithium resources have prompted extensive attention toward the development of other advanced battery systems. As a promising alternative to LIBs, potassium-ion batteries (KIBs) have attracted considerable interest over the past years owing to their resource abundance, low cost, and high working voltage. Capitalizing on the significant research and technological advancements of LIBs, KIBs have undergone rapid development, especially the anode component, and diverse synthesis techniques, potassiation chemistry, and energy storage applications have been systematically investigated and proposed. In this review, the necessity of exploring superior anode materials is highlighted, and representative KIB anodes as well as various structural construction approaches are summarized. Furthermore, critical issues, challenges, and perspectives of KIB anodes are meticulously organized and presented. With a strengthened understanding of the associated potassiation chemistry, the composition and microstructural modification of KIB anodes could be significantly improved.

State-of-the-art tendency, present critical issues and future opportunities of anode active materials in potassium ion batteries are systematically summarized.     

Ionic discotic liquid crystals: synthesis and characterization of pyridinium bromides containing a triphenylene core

Five novel pyridinium salts tethered with hexaalkoxytriphenylene molecules were synthesized by the quaternization of pyridine with ω-bromo-substituted triphenylene derivatives. Their chemical structures were determined by ¹H NMR, ¹³C NMR, IR, UV spectroscopy and elemental analysis. The thermotropic liquid crystalline properties of these salts were investigated by polarizing optical microscopy and differential scanning calorimetry. These triphenylene-based pyridinium salts with bromide as counterion were found to be mesomorphic over a wide temperature range.     

Recent applications of carbon-based nanomaterials in analytical chemistry: critical review

The objective of this review is to provide a broad overview of the advantages and limitations of carbon-based nanomaterials with respect to analytical chemistry. Aiming to illustrate the impact of nanomaterials on the development of novel analytical applications, developments reported in the 2005-2010 period have been included and divided into sample preparation, separation, and detection. Within each section, fullerenes, carbon nanotubes, graphene, and composite materials will be addressed specifically. Although only briefly discussed, included is a section highlighting nanomaterials with interesting catalytic properties that can be used in the design of future devices for analytical chemistry.     

Quinoline-8-ol-immobilized Amberlite XAD-4: synthesis,characterization, and uranyl ion uptake properties suitable for analytical applications

Amberlite XAD-4 has been functionalized by coupling it with 5-aminoquinoline-8-ol after acetylation. The resulting resin has been characterized by elemental analysis and IR spectra and has been used for preconcentrating uranyl ions prior to its determination by spectrophotometry. The optimum pH value for quantitative sorption is 4-6, and desorption can be achieved by using 5 mL of 1 mol L(-1) HCl. The sorption capacity of the resin is 11.5 mmol g(-1). The effect of various cations and anions on the preconcentration of uranium in conjunction with the determination procedure has been studied and we have found that none of the ions interfere except thorium. The enrichment factor for preconcentration of uranium was found to be 200. Ten replicate determinations of 40 micro g of uranium present in 1 L of sample gave a mean absorbance of 0.185 with a relative standard deviation of 2.64%. The detection limit corresponding to three times the standard deviation of the bank was found to be 2 micro g L(-1). The validation of the developed preconcentration procedure was carried out by successfully analyzing standard marine sediment reference material. The uranyl content of sediment and soils is estimated by spectrophotometry after its preconcentration with the above chelating resin.     

Ionic liquid catalyzed one-pot multi-component synthesis of fused pyridine derivatives: A strategy for green and sustainable chemistry

The synthesis of a combinatorial library of heterocycle-fused pyridine derivatives has been achieved successfully via a one-pot four-component reaction of aromatic/aliphatic aldehyde, malononitrile, thiazolidine-2,4-dione and ammonium acetate in the presence of piperidinium acetate as the catalyst. It involved the Knoevenagel condensation of the aldehyde and malononitrile to produce arylidene malononitrile as an intermediate, which was further intramolecular cyclization through Michael type addition ketone to the electrophilic double bond of the arylidene to produce fused pyridines in high yields. Environmental friendliness, low cost, Operational simplicity, extensive reusability and applicability, and easy recovery of the catalyst using simple evaporation are the critical features of this methodology. Also, a series of pyridine based dihydrothiazolo[4,5-b] pyridine-6-carbonitrile analogs were synthesized and selected for their in vitro antifungal and antibacterial activities.     

Photosensitized degradation of organic pollutants in water: processes and analytical applications

Photosensitized degradation has been used to remove a broad range of organic pollutants, generally with mineralization to CO₂ and other inorganic products such as Cl⁻ and . TiO₂ and Fe³⁺ are the photosensitizers mainly used to accelerate the degradation of persistent organic chemicals. Various analytical techniques were used to identify the degradation products and to monitor the degradation kinetics. Chromatographic techniques such as high-performance liquid chromatography (HPLC), gas chromatography (GC) and ion-exchange were used. Other analytical techniques, such as total organic carbon analysis, UV–visible spectrophotometry, spectrofluorimetry, and potentiometry, were also used. When the photodegradation is carried out in water, extraction methods such liquid–liquid extraction or solid-phase extraction need to be used, followed by GC or HPLC analysis. We review the analytical methods used for the identification of the products formed in photodegradation studies. Kinetic studies of the degradation are also reported.     

Fullerene-derivatized amino acids: synthesis, characterization, antioxidant properties, and solid-phase peptide synthesis

A series of [60]fullerene-substituted phenylalanine (Baa) and lysine derivatives have been prepared by the condensation of 1,2-(4'-oxocyclohexano)fullerene with the appropriately protected (4-amino)phenylalanine and lysine, respectively. Conversion of the imine to the corresponding amine is achieved by di-acid catalyzed hydroboration. The reduction of the imine is not accompanied by hydroboration of the fullerene cage. The [70]fullerene phenylalanine derivative has also been prepared as have the di-amino acid derivatives. The compounds were characterized by MALDI-TOF mass spectrometry, UV/Vis spectroscopy, and cyclic voltammetry. 1H and 13C NMR spectroscopy allowed the observation of diastereomers. Fullerene-substituted peptides may be synthesized on relatively large scale by solid-phase peptide synthesis. The presence of the C60-substituted amino acid in a peptide has a significant effect on the secondary structures and self-assembly properties of peptides as compared to the native peptide. The antioxidant assay of Baa and a Baa-derived anionic peptide was determined to be significantly more potent than Trolox.     

Molecular imprinting: a dynamic technique for diverse applications in analytical chemistry

Continuous advances in analyzing complex matrices, improving reliability and simplicity, and performing multiple simultaneous assays with extreme sensitivity are increasing. Several techniques have been developed for the quantitative assays of analytes at low concentrations (e.g., high-pressure liquid chromatography, gas chromatography, immunoassay and the polymerase chain reaction technique). To achieve highly specific and sensitive analysis, high affinity, stable, and specific recognition agents are needed. Although biological recognition agents are very specific and sensitive they are labile and/or have a low density of binding sites. During the past decade molecular imprinting has emerged as an attractive and highly accepted tool for the development of artificial recognition agents. Molecular imprinting is achieved by the interaction, either noncovalent or covalent, between complementary groups in a template molecule and functional monomer units through polymerization or polycondensation. These molecularly imprinted polymers have been widely employed for diverse applications (e.g., in chromatographic separation, drug screening, chemosensors, catalysis, immunoassays etc.) owing to their specificity towards the target molecules and high stability against physicochemical perturbations. In this review the advantages, applications, and recent developments in molecular imprinting technology are highlighted.     

Imprinted polymer particles for iron uptake: Synthesis, characterization and analytical applications

This work reports the preparation of molecularly imprinted polymer particles for selective extraction and determination of iron ions from aqueous media. The polymer particles were synthesized from Fe(NO₃)₃, morin, 4-vinylpyridine, ethyleneglycoldimethacrylate, and 2,2′-azobisisobutyronitrile and characterized by IR and DSC both prior to and after removing the Fe-morin complex by leaching with HCl. The effect of different parameters, such as pH, adsorption and desorption time, type and minimum amount of eluent for removing the complex from polymer was evaluated and optimized. The proposed method is characterized by the detection limit of 3.1 µg l^?1 anddynamic linear range of 25 to 200 µg l^?1, with the relative standard deviation less than 8.8%. The method was applied to the recovery and determination of iron ions in a few real samples.     

Dibenzoannelated tetrathienoacene: synthesis, characterization, and applications in organic field-effect transistors

Two structural isomers of six-fused-ring sulfur-containing molecules were synthesized as active materials for p-type organic field-effect transistors, and their optical and electrochemical properties were characterized. Field-effect transistors based on these compounds were fabricated to investigate the relationships between structures and semiconductor properties.     

Novel triptycene-derived hosts: synthesis and their applications in supramolecular chemistry

The development of new classes of macrocyclic hosts has always been one of the most important topics in supramolecular chemistry. During the past several years, based on the triptycene with unique three-dimensional rigid structure, several different kinds of novel triptycene-derived hosts including triptycene-derived cylindrical macrotricyclic polyether, triptycene-derived tris(crown ether)s, triptycene-derived molecular tweezers, triptycene-derived calixarenes, triptycene-derived heterocalixarenes, triptycene-derived tetralactam macrocycles and molecular cage have been designed and synthesized. Then, by exploring the applications of some of the triptycene derived hosts in molecular recognition and molecular assemblies, a series of new supramolecular systems with specific structures and properties have been developed. This feature article highlights our recent advances in the synthesis of triptycene-derived hosts and their applications in supramolecular chemistry.